MOS Single Stage Amp.

from Razavi

parameters need to be considered: transconductance gm, linearity, voltage swing, (small signal) gain Av.

common-source (CS).

1. CS with Resistive load

problems:
1.1 nonlinearity (gm is input-dependent, and furthermore voltage gain)
1.2. couldn't get stable gain because of difficulty in getting precise Rd (it's difficult
to fabricate resistors with tightly-controlled values or a reasonable physical \size)

trade off:
1. with constant input, to get high gain, Rd need to increase, however, this lead
to smaller voltage swing at the output (transistor could get into triode region),
also, this leads to greater time constant (Speed) at the output.

2. CS with Diode-connected load
2.1 Diode-connected load behaves like a two-terminal resistor (proof it and calculate the
equivalent resistance using small sig. model) 1/(gm +gmb) Parall. r0 . therefore, prob. 1.2 solved.
2.2 small signal gain Av = Vout/Vin is independent of input voltage and is a weak function of device dimensions, therefore 1.1 is partially solved.

Prob,
2.3 trade-off exists: increeasing load resistance limits output voltage swing.
2.4 gm is still nonlinear though

3.CS with Current Source Load (could be a current mirror)
3.1 it bears all adavantages of CS with diode-connected load.
3.2 output impedenace and minimum required |Vds| are less strongly coupled. Meaning r_top can be increased ( by increasing L) without too much concern of lowering V_ds_bottom into triode region.

Prob.
3.3 Voltage_drain is not well defined. need a feedback loop to froced it to a known value
3.4 Increasing L necessitates increasing W (otherwise, Vgs - Vth increases, for a given Drain current), which increase capacitance at the output node.
3.5 gm is nonlineart

4. CS Stage with Source Degeneration (Rs between Source_bot and ground)
4.1 Calculate Gm (I_drain/V_IN, not gm) , and when V_in is large, Gm approach to a specific value (1/Rs). prob 3.5 solved at large input voltage.
4.2 Output impedance is even larger (prove it)
4.3 for a specific input voltage, V_out is more stable (think about why )

Prob. 3.3, 3.4 persist

Transistor _mustknow

CMOS

un = 580 cm2/Vs
up = 0.4 un

pi - model
t - model

high input resistance of an amplifier to a signal is an advantage of MOSFET to BJT

07/14/2007

做梦

大雨
美国式平房
院子有很多树
树是绿色的
很瘦的猫
从QWQ那拿的VCR
要做什么也忘了
我从房子跑出来跑进去想要找到东西怎么都没找到
找什么
也想不起来了



这时候电话响了，是Liu胖子， ft

Newbie's speculations on Stock Market(1)-AMD

[AMD]

Fact1: [07/10/2007] former CEO of ATI and VP of AMD resigned.
Fact2: AMD chopped desktop CPU prices
Fact3:[07/10/2007] AMD to hold meeting with shareholders

my conclusion : sth is definitely wrong with AMD, stock price should go down (assuming more ppl would be less confident on AMD's future), which echoed from BBS, though contentions are always there.

Fact: from 07/11 to 07/12, stock of AMD increases from $14.44 to $15.36 instead.

Now, the question is: why?

Linux Command (1)

ps : check process status
kill : kill process
eg. kill 8505, 8505 being the process number checked by "ps"
jobs : check suspended work (suspended by "ctrl +z")
% : restart suspended job by "ctrl +z"
eg. %1 , "1" being the suspended job number
history : check command history
free /quota : check available space ? (not clear yet)
rm : remove file (delete)
eg. rm tr_test.sp
mkdir : make directory
cd .. : go to upper directory
kate : visual text editor under linux

vim (or vi) : text editor under linux
:w :save
:w + "file name" :save to a file name
:x :save and exit = :wq
:q : exit without save